Auckland Council is gearing up for its second planned aerial drop of 1080 in the Hunua Ranges.
The contentious pest control will put people and domestic pets at risk if they enter the ranges.
But Rachel Kelleher from the Hunua Project says she's seen huge benefits for native birds.
"We've got two of our best back-to-back breeding seasons ever," she told Newshub. "That's all largely as a result of the success of that 2015 operation."
Ms Kelleher says land owners are increasingly opting for 1080 drops.
"We understand and accept there is a range of views around pest management, but we've also got a huge amount of support."
The process begins with dropping non-toxic bait to give pests like possums, rats and stoats the taste for it. Then the real stuff gets distributed.
"As expected, in the three years since the last operation the numbers of pests has begun to creep up again," Councillor Penny Hulse said last week.
"By repeating pest control we can ensure the protection of our precious forest and the threatened species that live within it."
The parks will be closed during the operation and a track clearance programme carried out before they are reopened.
The council says 1080 is particularly toxic to mammals, so is useful for protecting native birds because New Zealand's only native mammals are bats.
This drop will see around 2kg of bait dropped per hectare, containing about a teaspoon's worth of the poison. This is less than in 2015, when 2.5kg per hectare was dropped.
A report in 2011 by the Parliamentary Commissioner for the Environment backed 1080's use.
Newshub.
